This study aimed at estimating the brightness of a monochromatic LED point source as perceived by the elderly and protanopes. To estimate the perceived brightness of the monochromatic LED point source for the elderly and protanopes, we defined an index, brightness perception efficiency, which is a ratio of perceived luminosity with spectral luminous efficiency of the elderly or protanopes to the luminosity with standard spectral luminous efficiency. The brightness perception efficiency was calculated using both the LED spectral radiant intensity defined by a peak wavelength and a full width at half maximum (FWHM) of the LED and the spectral luminous efficiencies of the elderly in their 70s and protanopes. The brightness perception efficiency indicated that monochromatic LED point sources with a broad FWHM effectively attenuated the reduction in perceived brightness of the elderly and protanopes. It is expected that in the case of a peak wavelength of 475 nm the elderly perceive brightness equivalent to 1.6 times the luminosity for the LED with a FWHM of 100 nm compared to that with a FWHM of 15 nm. In the case of a peak wavelength of 635 nm protanopes perceived brightness equivalent to about 3 times the luminosity for the LED with a FWHM of 100 nm compared to that with a FWHM of 15 nm. Based on the brightness perception efficiency, we developed an LED illumination simulator that allows young observers with normal color vision to experience the brightness perceived by the elderly and protanopes.
New illuminants, such as LEDs or OELs that can vary their own color, are expected to spread. The opportunities when colored lights are used in lighting are currently increasing. Research on the impression of rooms by the colored light used in the lighting is important knowledge about the adaptation transition at the change of the lighting between chromatic colors. This paper reports the results about the duration necessary for steady adaptation based on the color appearance of the light when the light color changes between chromatic and white. The duration of the necessary adaptation to white light from some chromatic light is shorter than that to chromatic light from white light. The duration of adaptation to chromatic light from white light and that to white light from chromatic light becomes longer with vivid chromatic light.
In the field of colorimetry, metamers are color stimuli with the same tristimulus values but different spectral power distributions. In general, we perceive the metamers as the same color. However, when we observed white light source metamers consisting of a high intensity discharge lamp (HID) and a white LED, they were perceived as different color. To investigate the color appearance of these white light sources, we carried out color matching experiments. These white light sources were presented respectively as a reference stimulus. A mixture of light from a red LED, a green LED, and a blue LED was used as a matching stimulus to match its color and brightness appearance with a reference stimulus. In the case of the white LED, the chromaticity coordinates derived from trichromatic matches were distributed nearby that of the reference stimulus. On the other hand, in the case of the HID, chromaticity coordinates derived from trichromatic matches were distributed in a 700K higher color temperature area than that of the HID reference stimulus. In this paper, we discuss the cause of color mismatch between colorimetric matching with relation to the variety of color matching functions.
Proposed in this paper is a visibility evaluation method applicable for any complicated situation. It is applicable, if a luminance image with a target is obtained, to any kind of targets, namely both luminous and reflective targets, to any shape of targets, to targets with non-uniform luminance, and to targets with any complicated luminous background. This method is based on the multi-channel model of our visual system and uses an orthogonal wavelet transform with symlet 6 as the mother wavelet. The method can generate a Visibility Evaluation Image from a luminance image with a target, based on the contrast sensitivity functions of various average luminances. VEI illustrates the visual edges of any objects in the luminance image. The value indicated in the VEI can be represented by using multiples of the threshold level and by using the subjective visibility levels. The VEI for a person with a specific visual performance can be generated if his/her contrast sensitivity functions are provided.
The impression for the room and the color appearance of objects are different with the more colorful light colors that have recently been released. When the light colors appropriate to each residential room are used, residents are exposed to the change when they move from a room to another of different light colors. Residents' impressions due to the change in light colors have to be considered. In this study, paying attention to the light colors and the color adaptation, and the influence of them on the impressions is grasped. The consideration compared the difference in the chroma and hue of the light colors for each impression. In the transitional process of impression, there are different impressions from those of the static conditions, and the processes are classified into some patterns. In the transitional process the condition includes a transition of color light from daylight and daylight from color light. The consideration compared the combination of these conditions. As a result, "the light colors" and "the change in light colors" influenced the impressions.
The prediction method of melatonin suppression values was based on previous studies related to melatonin suppression and pupil constriction. Estimated values that considered pupil constriction were larger than the actual suppression values. We focused on the pupil constriction and its correction factor to interpret the action spectrum for the properties of the melatonin suppression model. When the correction factor was used to modify the model, actual suppression values were almost completely predictable. These factors suggest that it might be possible to explain the indescribable results.
Two kinds of the cold cathode fluorescent lamps (CCFLs) were operated at 5mA as a life-test with Ni plate electrodes. One kind of CCFL contained Ne-Ar-Hg (Hg CCFL) and the other contained Ne-Ar (Hg-less CCFL). The results of the operations showed that the Hg CCFL's voltage decreased with operating time continuously. On the other hand, the voltage of the Hg-less CCFL began to increase and its emitting light color changed from light violet to strong red after about 6000 hours operating time. The V-t and I-t waveforms of the Hg CCFL did not change during the life test, while those of the Hg-less CCFL at 6000 hours were different from those at 8000 hours. The wave form data seem to show that the Hg CCFL's discharge was glow mode and that the Hg-less CCFL discharge changed from glow mode to arc mode after 6000 hours operating time. The authors then observed the electrodes of both kinds of lamps at 8500 hours operating time. The shape of Hg CCFL's electrode at 8500 hours was the same as at 0 hours, but that of the Hg-less CCFL at 8500 hours was very different from at 0 hours. The tip of Hg-less CCFL's electrode at 8500 hours operating time was gouged and U-shaped. The data show that the reason for the gouging of the electrode at lamp life end, or in very low temperature operation, was the sputtering of rare gases caused by the depletion of Hg.
The integrating sphere and hemisphere are useful for measuring optical radiation. To use and design it for a particular application, it is important to understand how the integrating sphere works. The theory of the integrating sphere and hemisphere are based on the theory of radiation exchange within an enclosure of diffuse reflecting surfaces. In this paper, the theory and error functions of the integrating sphere and hemisphere are discussed.